Composite refractory brick



July 1, 1930. J MQRGAN 1,769,708 I COMPOS ITE REFRACTORY BRICK FiledOct. 10, 1927 gvwewtoz JOHN D. MoRsA/v 851;; /1 i s a t tow;

Patented July 1, 1930 S '\UN ITEDS STATES .PATELNT OFFICE JOHN D.MORGAN, OF MAPLEWOOD, NEW JERSEY, ASSIGNOR TO DOHERTY RESEARCH 7COMPANY, OENEW YORiK, N. Y.,

A CORPORATION OF DELAWARE' COMPOSITE REFRACTORY BRICK Application filedOctober 10, 1927.. Serial No. 225,187.

The present invention relatesto the production of a composite furnacewall, to a brick suitable for making a furnace .wall of compositecharacter and to a method of making a composite brick.

It has been proposed to make furnace walls of a composite character toreduce the large N t1on to provide acomposite wall having high radiationlosses common when the furnace Walls are of ordinary firebrick and redbrick. m It has been found that decreasing the radiation from thefurnace walls has increas'ed'the average temperature inthe furnace andhas increased the rate of deterioration of-the firebrick. T It has beenproposed also to use furnace linings of'high refractory character incomposite walls to permit the use ofhigh temperatures. experienced inobtaining a-durable wall havin 'a'highly refractory lining.- go %)ne ofthe refractory materials which it has been'proposed to use'as a coatingfor furnace bricks and as a layer liningior furnaces is carborundum.Carborundum, however, although very refractory, is highly con- 5-ductive at high temperatures. Consequent- 131, if it is attempted topush the average furnace temperature much above that commonly employed,the heat insulating materialin contact with the carborundum layer isapt" to swell or soften, leading unless thecarborundum' layer is verythick, to the early destruction of the'connection or bond between thecarborundumlayer. audits backing. As carborundum is'relativelyexpensive, it is impractical to employ it in thick layers and its use inheat insulated furnaces has been very I limited.

Another: material which it has been pro posed to useas a refractorylining for fur- 40 naces, is zirconia Th s'material does not transmitheat as-read1ly as carborundum,

but it changes in volume when heated under ordinary furnace conditionsmuch more than a most refractories and much more than the -materialsdesirable for use as backmgs for the zirconia. Consequently, the bondbetween the zirconia and its backing is soon weakened and the zirconiadisplaced from the furnace wall. No serious attempt has been made to usezirconia linings in commercial furnaces.

It is one of the objects of the present invenheat insulating capacityand adapted for use in commercial furnaces.

Other objects and advantages of the present invention will hereinafterap ear.

In the drawing forming part of the present disclosure, the figur'e is aperspective view of a portion of a furnace wall according to the presentinvention. However, difliculty has been It is advantageous to be able tobuild a fur-, nace or other wall of bricks. It is preferred therefore toapply the present invention to bricks or furnace walls built'of bricks,but it is. not limited thereto.

In said figure, 10 indicates a portion of a vertical furnace wallaccording to the present invention. Said wall is laid up of bricks 12-12of any convenient or desired size and preferably of the ordinaryrectangular shape.

Walls 10 may have an outer metal casing 13 thereon if desired. The mainbody portion of bricks 12 is of a heatinsulating material, preferablydiatomaceous earth. However, puffed clay, cellular zircon, zirconia, orclay may be used as the material for the main body portion of thebricks. Ordinary plastic clay, although making bricks of much higherheat insulating capacity than fireclay, can be used as the material forthe body of the bricks only when a refractory layer of high heatinsulating capacity is used on the face of the bricks to be exposed tofire. Each of the bricks 12 has a surface layer 14 attached 'to the mainbody portion of the brick along a plane 16. The loricks 12 are so placedin the furnace wall that the layers 14 all face in one direction or, inother words, lie along the vertical face of the wall on the side towardthe furnace chamber. The layers 14 are of a highly refractorycomposition and preferably also of non-conductive characteristic. Zircon(native zirconium silicate) is the preferred material from which to formlayers 14. This material has been further desirable characteristic ofbeing free from either permanent, growth or permanent shrinkage u onbeing heated to high temperatures. here is therefore no material changein the volume of the -material forming the facing over long periods ofuse. But few other refractory materials possess this characteristic,these being such substances as electrically fused magnesia, electricallyfuzed quartz, electrically fused chromium oxide, and similar products ofthe electric furnace. It will be understood that by substantiallyconstant volume material as used in the following specification andclaims such refractories are intended. Zirconia may be used only ifmixed with sufficient zircon to prevent the zirconia from shrinking somuch when the bricks are heated in use as to weaken the layers 14 or thebond between the layers and the main portion of the bricks.

The bricks 12 may be fired in two parts and the arts cemented togetheror they may be fired all in one piece.

If the bricks are to be fired in two parts, the body portions of thebricks 12 are formed,

forexample,of diatomaceous earth or of a clay which is capable ofpufiing when burned and then fired to at least 2500 F. Bonded plates 14of highly refractory non-conductive, nonswelling material such as zirconor zirconzirconia are then formed, preferably of about one inch inthickness, and including a sui-table bonding agent such asless than oneper cent of a precipitated hydroxide, a few percent of ortho hosphoricacid or less than one percent 0 precipitated carbonate. -The platesare'then fired. The preferred temcounter in use. The hydroxide andcarbo-' nate bodies, of course, decompose when heated and the bondingaction is due directly to their decomposition products. Precipitatedbarium carbonate gives good results. After the plates have been fired,the plates 14 are then cemented to the body portions of bricks 12 byplacing powdered boro-silicate enamel,

or the like, betweenadja'cent faces of the body portions and the platesand heating the body portions and plates to fuse the enamel and to bondor cement the plates to the body kiln will permit. It is good iportions. A brick having a sil-o-cel porous silica body and a zircon capcemented on one of its faces by a fused silicate as just described hasbeen tested by applying an oxyacetylene flame to the center of the capuntil the cap had reached a high temperature. No alteration of thesurface of the cap was observed as a result of this test and the capremained firmly united to the porous body. If the bricks are to be firedin one piece, the bonds between the high refractory layers 14 and thehigh insulating body portions of bricks 12 may be made at the same timeas the two refractories themselves are bonded.

For example, the body ortions of the bricks 12 may be formed ofiatomaceous earth or crushed puffed clay togetherwith a binder and thehigh refractory layers 14 formed .of zircon grain or a mixture of zirconand zirconia together with a binder or bond supplying agent. Preferablythe body portions are formed with the same hinder or bond-supplyingagent as the high refractorylayers 14, and the two assembled to formbricks while still moist. Either of the bonding agents mentioned aboveis suitable for the entire brick. Upon drying and subsequent firingtheinsulating body portions and high refractory layers 14 are bondedtogether with out any definite plane of cleavage between them, thelayers 14 being integrally united to the body of the bricks by a commonbonding substance which extends throughout the entire mass of the brick.The resulting bricks 12 are highly resistant to thermal and mechanicalshocks tending to separate the layers from the bodies under furnaceconditions. In this case also it is desirable that the firingtemperature reach 2500 F.

i It has been found that a wall made up according to the presentinvention having a layer of zircon one inch thick backed bya stances, ithas been found that the zirconium compounds, such as zircon and zirconiawhich contain oxygen as well as zirconium, resist spalling and crackingunder furnace conditions to a notable degree and that they sustain ahigher load at high temperatures than other materials which have aheat-insulating effect at high temperatures of a higherorder than theordinary fire-brick. Also, while it is preferred to use these zirconiumrefractories on bodies of material having higher heat-insulating effectat at high temperatures than fire-brick, the invention is not limited tothis.

Having thus described my invention, I

claim zirnonium compound firmly attached to a body of refractorynon-conducting material, saidlayer and body being bonded throughout bythe same bonding material.

5. As an article of manufacture, a composite brick having a layer ofrefractory, substantially constant volume, non-conducting materialfirmly attached to a non-conducting body of diatomaceous earth, saidlayer and body being bonded throughout by the same bonding material.

6. As an article of manufacture, a composite brick having a layer ofhigh refractory, substantially constant volume, non-conducting materialfirmly attached to a non-conducting body of non-conducting material,said layer and body being bonded throughout by the products ofdecomposition of precipitated barium carbonate.

7. As an article of manufacture, a compos- Jite brick having a layer ofsubstantially constant volume zircon material firmly attached to anon-conducting body of diatomaceous earth, said layer and body beingbonded throughout by the products of decomposition of barium carbonate.

8. As an article of manufacture, a composite brick having a layerofzircon firmly atconstant volume, I

to withstand high temperatures Without sep a ration.

14. A furnace Wall having a layer of highly refractory substantiallyconstant volume non-conducting material of high heat-insulating capacityas a facing for a body portion of refractory material of higherheat-insulating capacity and less refractivity than said layer.

In testimony whereof I affix my signature.

JOHN D. MORGAN.

tached to a refractory non-conducting body.

9. As an article of manufacture, a compos ite brick having a layer ofzircon firmly attached to a body of diatomaceous earth, said layer andbody being bonded throughout with the same bonding material. a

10. As an article of manufacture, a composite brick having a zirconlayer and a body of diatomaceous earth, said layer being cemented tosaid body by a silicate bond.

11. The article as set forth in claim' 10 in which the cementing bond isa boro-silicate.

12. A comoosite brick having a facelayer of substantially constantvolume zircon composition firmly attached to a body portion of

